Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic...
-
Upload
tyler-pawling -
Category
Documents
-
view
221 -
download
5
Transcript of Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic...
![Page 1: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/1.jpg)
Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction
Shule Li, Adam Frank, Eric Blackman University of Rochester, Department of Physics and Astronomy. Rochester, New York 14627
A Panel of Simulation Images?
![Page 2: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/2.jpg)
1. Previous works on MHD shocked clump simulations2. Description of the problem3. Goals and methods of the current study4. Table of Runs5. Simulations of MHD clumps with external magnetic field6. Simulations of MHD clumps with contained magnetic field7. Discussion and conclusion
Introduction
Outline
Problems involving magnetized clouds and clumps, especially their interaction with shocks are common in astrophysical environments and have been a topic of research in the past decade. The magnetic field structure, whether aligned with the shock or perpendicular to the shock, can have profound influence on the shocked behavior and evolution of the clump. Most previous numerical studies have focused on the scenario where the shocked clump is immersed in a uniform background. In this presentation we take one step further to assume a more realistic scenario wherethe clumps have the tangled magnetic field residing inside. These clumps can be formed when winds blowing through a magnetized clumpy background medium detach the medium along with the field lines. We will show that the contained magnetic field can have great influence on the post-shockclump evolution. Some of them may lead to observational evidence of the magnetic field structure inthe interstellar medium.
![Page 3: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/3.jpg)
Sonic Mach number:
Density Contrast:
Alfvenic Mach number:
Magnetic Beta:
Clump crushing time:
clum p
am b
rc
r=
,
w ind
s am b
uM
c=
w indA
a
uM
v=
2,
2
2 s am b
a
c
vb
g=
1/ 2clum p
ccw ind
r
u
ct =
Meaningful Quantitieswind
ambientclump
Problem Description
![Page 4: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/4.jpg)
Previous Results: Hydrodynamic Clumps
![Page 5: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/5.jpg)
Density log plot at 2τcc (top) and 6τcc (bottom). Left: β = 4. Right: β = 256.
Field line plot at 2τcc (top) and 6τcc (bottom). Left: β = 4. Right: β = 256.
When the external field is parallel to the shock propagation direction:
No significant difference in terms of density evolution even for β = 1.
The criterion for the magnetic field removing K-H instabilities at the clump boundaries is: β < 1 along the boundary. The criterion for the magnetic field to stabilize R-T instabilities is roughly: β < χ/M.
But there is no place that themagnetic field becomes energetically dominant; that is, almost everywhere β >> 1.
Magnetic fields stretched over the top of the clump can have a significant stabilizing influence that improves the flow coherence.
Jones, T.W., Ryu, Dongsu, Tregillis, I.L. 1996 ApJ, 473, 365
Previous Results: Clumps with a Uniform External Magnetic Field
![Page 6: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/6.jpg)
Density log plot at 2τcc (top) and 6τcc (bottom). Left: β = 4. Right: β = 256.
Field line plot at 2τcc (top) and 6τcc (bottom). Left: β = 4. Right: β = 256.
When the external field is perpendicular with the shock propagation direction:
The magnetic field is stretched and wrapped around the clump, which effectively confines the clump and prevents its fragmentation, even for moderately strong field β = 4. The clump embedded in the stretched field is compressed, but then, because of the strong confining effect of the field develops a streamlined profile and is not strongly eroded.
The magnetic pressure at the nose of the clump increases drastically, which acts as a shock absorber.
At later stage, the stretched field around the clump edge has β < 1 even for moderately strong initial field condition. This protects the clump from further disruption.
Jones, T.W., Ryu, Dongsu, Tregillis, I.L. 1996 ApJ, 473, 365
Previous Results: Clumps with a Uniform External Magnetic Field
![Page 7: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/7.jpg)
With radiative cooling added to the simulation,people found that the shocked behavior of clumps can change drastically comparing to the addiabatic cases.
Bow shock and transmitted shock have differentcooling time. This fact divides the parameterspace into 4 different regimes.
Thin fragments which are dense and cold are developed after shock.
The boundary flows are streamlined when the bow shock cools efficiently.
Balk of cooled clump material tightly boundedby the bow shock is formed when transmitted shock cools efficiently.
The clump behavior depends heavily on actually cooling routine implemented in the simulation Code.
Fragile et al (2005 ApJ 619, 327)
Previous Results: Clumps with External Magnetic Field and Radiative Cooling
![Page 8: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/8.jpg)
3D density contour at various clump crushing time for weak and strong aligned field.
3D density contour (left) and magnetic pressure (right) for weak aligned field, perpendicular field, and oblique shock cases, at 4τcc.
Min-Su Shin, James M. Stone, Gregory F. Snyder, 2008 ApJ, 680, 336
Previous Results: 3D Simulations on Shocked Clumps
![Page 9: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/9.jpg)
Methodology
A Panel of Image of the Day?
AstroBEAR is a parallelized hydrodynamic/MHD simulation code suitable for a variety of astrophysical problems. Derived from the BearCLAW package written by Sorin Mitran, AstroBEAR is designed for 2D and 3D adaptive mesh refinement (AMR) simulations. The 2.0 version of the code shows good scaling in various tests up to 2000 processors. Users write their own project modules by specifying initial conditions and continual processes (such as an inflow condition). In addition, AstroBEAR comes with a number of multiphysical processes such as self gravity and thermal conduction, pre-built physical phenomena such as clumps and winds that can be loaded into a user module.
![Page 10: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/10.jpg)
Methodology
MHD Equations
with
Radiative cooling is implemented via operator splitting, with several built-in cooling tables.In the presented simulations, we use Dalgano-Mcray cooling table.
![Page 11: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/11.jpg)
Table of Runs
Field Strength(Magnetic β)
Field Structure Orientation(Relative to
Shock Direction)
Power Spectral index
BX1 0.5 External, Uniform
‖ -
BX2 8 External, Uniform
‖ -
BY1 0.5 External, Uniform
┴ -
BY2 8 External, Uniform
┴ -
BCTP 0.1 Contained, Toroidal Only
┴ -
BCTA 0.1 Contained, Toroidal Only
‖ -
BCPP 0.1 Contained, Poloidal Only
┴ -
BCPA 0.1 Contained, Poloidal Only
‖ -
BCRF1 0.1 Contained, Random
- 0
BCRF2 1 Contained, Random
- 0
BCRK1 0.1 Contained, Random
- -11/3
BCRK2 1 Contained, Random
- -11/3
Clump Density Contrastχ = 100
Ambient Densitynamb = 1 cc
Ambient TemperatureTamb = 10 K
Clump RadiusR = 150 AU
Shock Mach M = 10
Simulation Parameters
-1
4
![Page 12: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/12.jpg)
![Page 13: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/13.jpg)
MHD clumps with External Magnetic Field
http://www.pas.rochester.edu/~smurugan/
![Page 14: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/14.jpg)
MHD clumps with Contained Magnetic Field
Case BCTP
http://www.pas.rochester.edu/~shuleli/HedlaMovie/torzvr.gif
![Page 15: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/15.jpg)
MHD clumps with Contained Magnetic Field
Case BCTA
http://www.pas.rochester.edu/~shuleli/HedlaMovie/torxvr.gif
![Page 16: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/16.jpg)
MHD clumps with Contained Magnetic Field
Case BCPP
http://www.pas.rochester.edu/~shuleli/HedlaMovie/polzvr.gif
![Page 17: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/17.jpg)
MHD clumps with Contained Magnetic Field
Case BCPA
http://www.pas.rochester.edu/~shuleli/HedlaMovie/polxvr.gif
![Page 18: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/18.jpg)
MHD clumps with Contained Magnetic Field
50% Cut Movies
http://www.pas.rochester.edu/~smurugan/
![Page 19: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/19.jpg)
MHD clumps with Contained Magnetic Field
Special Case: Toroidal Combined with Poloidal
http://www.pas.rochester.edu/~shuleli/HedlaMovie/tp1vr.gifhttp://www.pas.rochester.edu/~shuleli/HedlaMovie/tp2vr.gif
![Page 20: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/20.jpg)
MHD clumps with Contained Magnetic Field
Discussion and Conclusion 1: Ordered Field
![Page 21: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/21.jpg)
MHD clumps with Contained Magnetic Field
Discussion and Conclusion 1: Ordered Field
![Page 22: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/22.jpg)
MHD clumps with Contained Magnetic Field
Discussion and Conclusion 1: Ordered Field
![Page 23: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/23.jpg)
MHD clumps with Contained Magnetic Field
Discussion and Conclusion 1: Ordered Field
![Page 24: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/24.jpg)
MHD clumps with Contained Magnetic Field
Case BRF1, BRF2
![Page 25: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/25.jpg)
MHD clumps with Contained Magnetic Field
Case BRK1,BRK2
http://www.pas.rochester.edu/~shuleli/HedlaMovie/kolsvr.gif
![Page 26: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/26.jpg)
MHD clumps with Contained Magnetic Field
Magnetic Energy Line Plots: Ordered Field
![Page 27: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/27.jpg)
MHD clumps with Contained Magnetic Field
Magnetic Energy Line Plots: Random Field
![Page 28: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/28.jpg)
MHD clumps with Contained Magnetic Field
Kinetic and Thermal Energy Line Plots
![Page 29: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/29.jpg)
MHD clumps with Contained Magnetic Field
Mixing Ratio Line Plots
![Page 30: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/30.jpg)
MHD clumps with Contained Magnetic Field
Mixing Ratio Line Plots: Different Beta
![Page 31: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/31.jpg)
MHD clumps with Contained Magnetic Field
Vorticity Line Plots
![Page 32: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/32.jpg)
MHD clumps with Contained Magnetic Field
Power Spectrum Line Plots
![Page 33: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/33.jpg)
MHD clumps with Contained Magnetic Field
Discussion and Quantitative Result
![Page 34: Clumps With External Magnetic Fields, Their Interaction With Shocks, and the Effect of Magnetic Thermal Conduction Shule Li, Adam Frank, Eric Blackman.](https://reader035.fdocuments.in/reader035/viewer/2022062421/56649cbf5503460f94985270/html5/thumbnails/34.jpg)
MHD clumps with Contained Magnetic Field
Conclusion 2: From Line Plots